In the field of NMR spectroscopy, a sample is surrounded by an NMR probe that consists of a radio frequency (RF) coil tuned to generate a field at a desired excitation frequency and receive a return NMR signal. The spectrometer typically consists of a large magnet that generates a static magnetic field, and that surrounds a sample region of the spectrometer. A sample is located in a discrete sample tube and introduced to the sample region of a probe assembly. The probe assembly includes a housing that fits within the magnet bore, and that contains the RF coil. For a probe that uses a single RF coil, the coil typically surrounds the sample tube when the sample is introduced to the probe, and generates an RF pulse that induces a return NMR signal from the sample that is detected using the RF coil.
When analyzing a fluid sample with an NMR spectrometer, the sample is typically sealed within a sample tube. The tube is then introduced to the probe of the spectrometer, so as to locate the sample tube in the appropriate sample region. By proper activation of the RF coil, and detection of the resulting NMR signal, an NMR spectrum is compiled. The sample tube is then removed, and a new sample tube introduced to the probe. This process of testing one sample tube at a time is effective, but is highly laborious and time-consuming.
Certain prior art NMR spectrometers have been constructed in the past that use a sample container that allows a liquid sample to flow into and out of the container while the probe is positioned in the probe in the bore of the NMR magnet. This allows new samples to be introduced to the sample region without having to remove the sample tube and introduce a new one. Typically, however, these flow-though sample cells are fragile and expensive to replace. Moreover, such flow-through sample tubes are simply placed into a probe intended for discrete sample tubes. For example, a dual-function NMR probe has been described in U.S. Pat. No. 6,396,274 which allows a user to convert the probe operation between stationary sample tubes and a flow-through sample tube. In this system, a flow cell may be located in the NMR probe in a space surrounded by an RF coil. The flow cell may also be removed, and a discrete sample tube located in the same space.